I tried installing build 18362.30 and recreated the .NET issue. I let it upgrade to the latest CU, but .NET remained broken.
I then upgraded to 18912, using the ISO. That fixed .NET. Once I confirmed that .NET was there and I had PowerShell working, etc., I rolled back to 18362.175. However, .NET was again broken.
So, if the only way to fix .NET is to upgrade to 18912, you may have to keep running that until Spring 2020.
However, for most, a clean install of Windows 10 version 1903 will auto-update during install to build 18362.175 and .NET will work properly. If a clean install is an option, I would try that instead of using the Insider builds.